Concrete production facilities add iron oxide pigments or other additives to concrete to color concrete, to add other attributes to concrete, or to otherwise beautify and increase value to the finished product. Iron oxide pigments or other concrete additives are available in powder, liquid, and granular forms. A granular form of additive is an additive formed into pellets, grains, or granules as opposed to a powder. Some concrete producers use automated color dispensers for dispensing iron oxides or other additives into the concrete mixer in order to reduce labor and increase consistency. Currently on the market there are systems to dispense powder, liquid, and granular additives.
Powder systems are too slow to keep up with modern concrete production requirements. Powder color or other powder additives have a tendency to “bridge” or clump up, making it difficult for the powder to flow through pipes and bins. Vibrators tend to pack the powder in the bins, so high voltage augers are used. Occasionally, bridge “breakers” are added to help the powder flow through the bins. In many cases, powder pigment cannot be dispensed into concrete at the point of production due to these issues. Dust control may also be required for automated powdered color pigment.
Liquid color is produced by blending powder iron oxide, water, and chemicals. Liquid color requires an average of 40% higher dosage by weight than powder or granular color to compensate for the liquid, primarily water, in the pigment formula. A liquid color mixture should be kept in a temperature-controlled environment to prevent freezing and drying of the product. A liquid color mixture should also be recycled regularly to prevent settling. Accordingly, it is often difficult to use liquid color mixtures at a job site.
Granular pigment is also produced from powder pigment. The purpose of producing the granular form is usually for automation in material handling. Granular pigment does not bridge or clump like powder pigment, and with minimal vibration or agitation, the granular pigment flows easily. There are some granular systems in the market, and some of these systems use 3-phase, high-voltage power and are very slow. Other granular systems dispense the pigment pneumatically through air pressure, which can be a major burden on the concrete production equipment, such as the plant's air compressor system. Dispensing the granular pigment in dry form directly into a cement mixer can also cause some dispersion issues, causing lower tint or color strengths in the finished concrete. Thus, efficient and economical systems and methods for mixing granular pigment with cement at a job site are presently unknown.